Information Notice 1993-75, Spurious Tripping of Low-Voltage Power Circuit Breakers with GE RMS-9 Digital Trip Units
UNITED STATES
NUCLEAR REGULATORY COMMISSION
OFFICE OF NUCLEAR REACTOR REGULATION
WASHINGTON, D.C. 20555 September 17, 1993 NRC INFORMATION NOTICE 93-75: SPURIOUS TRIPPING OF LOW-VOLTAGE POWER CIRCUIT
BREAKERS WITH GE RMS-9 DIGITAL TRIP UNITS
Addressees
All holders of operating licenses or construction permits for nuclear power
reactors.
Purpose
The U.S. Nuclear Regulatory Commission (NRC) is issuing this information
notice to alert addressees to the potential for loss of safety-related buses
or individual loads because of spurious tripping of low-voltage circuit
breakers fitted with General Electric (GE) RMS-9 digital trip units. It is
expected that recipients will review the information for applicability to
their facilities and consider actions, as appropriate, to avoid similar
problems. However, suggestions contained in this information notice are not
NRC requirements; therefore, no specific action or written response is
required.
Description of Circumstances
In October 1992, the Tennessee Valley Authority (TVA) reported to the NRC
pursuant to Part 21 of Title 10 of the Code of Federal Regulations (10 CFR
Part 21) that the ungrounded, delta-connected, 480-volt distribution system at
its Browns Ferry Nuclear Plant (BFN) had experienced short-duration, high- amplitude current transients (possibly high-frequency electrical noise spikes)
that caused unwanted tripping of some GE AK-type circuit breakers fitted with
GE RMS-9 solid-state digital trip units. These units have a low-pass filter
(described by some as a "holdoff circuit") that is supposed to exclude most
transients of this sort. However, TVA reported that testing of the trip units
revealed that the instantaneous trip function of the trip unit would respond
to current transients as short as 100 microseconds and trip the breaker when
the peak amplitude of the current pulse or spike was sufficiently above the
instantaneous trip setpoint of the RMS-9 unit.
On August 4, 1993, the NRC was informed that the Maine Yankee Nuclear Power
Plant had a similar situation that the licensee described as sympathetic
tripping of two safety-related, RMS-9-equipped breakers, one of which was a
load breaker (with longtime and instantaneous trip functions) and the other a
motor control center (MCC) feeder breaker (with longtime-shorttime trips).
Both of the affected breakers were fed from the plant's delta-connected,
480-volt, engineered safeguards buses which are of an ungrounded design like
9309140046 PoD . o
v-I
IN 93-75 September 17, 1993 those at Browns Ferry. The trips may have been initiated by current spikes
caused by an intermittent ground fault on the boric acid makeup tank startup
heaters, a nonsafety-related load on that bus; although their breaker did not
trip. Also, the trips occurred during the process of ground isolation which
may have created or contributed to transients on the busses. However, the
transients were not sufficient to trip other RMS-9-equipped breakers, some of
which, acting as Class IE isolation devices, are meant to protect the safety- related busses from faults and overloads on nonsafety-related circuits, which
are also not environmentally qualified.
Discussion
In both these cases, the digital RMS-9 units were installed in GE AK-type low- voltage power circuit breakers as conversion kits to replace either earlier
versions of solid state units or the electromechanical EC-type series overload
trip units previously used. According to the manufacturer, GE Electrical
Distribution and Control (ED&C) in Plainville, Connecticut, the RMS-9 digital
electronic units were first available in October 1986 and the last of the
previous models, the analog electronic "MicroVersatrip" MVT-9 units, were
supplied in about January 1987.
GE Nuclear Energy (GE NE) in San Jose, California, has informed the NRC that
it is developing a modification specifically for the affected RMS-9 units at
Browns Ferry ta-makeathem-less-susceptible to unwanted tripping due to these
transients. In addition, ED&C is undertaking a systems study in cooperation
with GE NE and Maine Yankee to determine the conditions conducive to these
transients and to develop long-term or permanent solutions. These may be
software and/or hardware modifications to the trip units and/or recommended
modifications to the plant systems to prevent the unwanted tripping. Once
fully developed and tested, any trip unit updates would be included in new
RMS-9 units and GE switchgear service shops would install them in existing
units. Trip units could then be interchanged in breakers in the field or
purchased with new or replacement breakers.
Neither GE NE nor GE ED&C has issued any Service Information Letters (SILs) or
Service Advice Letters (SALs), respectively, on this subject as yet. However, GE product literature indicates that the units can be set up with their
instantaneous trip functions disabled. This may be more appropriate for
certain applications (typically, feeder breakers) which, for purposes of
breaker coordination, would rely on a short time trip function for fault
protection, keeping the instantaneous trip functions only on load breakers.
The NRC is attempting to obtain sufficient information to better define the
range of applications of these units, envelop the conditions likely to make
the equipment susceptible to the problem, and identify any common-mode
initiators that may exist. GE has confirmed that its evidence suggests that
ungrounded systems (particularly if delta-connected) are apparently the most
susceptible to the kind of transients to which the RMS-9s can respond. RMS-9 units, used only on low-voltage switchgear, are used in certain models of GE
-J
IN 93-75 September 17, 1993 molded-case circuit breakers, and "Power Break" circuit breakers in addition
to the metalclad breakers. Although, none except those on metalclad air
circuit breakers have reportedly experienced this problem, other RMS-9s may
not have been exposed to the transients of concern. Meanwhile, GE NE and the
GE Switchgear Apparatus Service Shop in Atlanta, Georgia, are currently
assisting Maine Yankee in exchanging (at least temporarily) several critical
RMS-9-equipped breakers for ones fitted with EC-type series trip units.
In terms of safety significance, these incidents of spurious tripping, although somewhat isolated, raise the concern that a common-mode initiator of
intermittent ground faults on nonsafety-related and unqualified circuits, such
as a loss-of-coolant accident or high-energy line break, could conceivably
cause propagation of current spikes to multiple portions of an electrical
distribution system. They may not trip Class IE isolation breakers not fitted
with RMS-9s, and may not trip some with RMS-9s, but could result in unwanted
tripping of other RMS-9-equipped breakers and the attendant loss of vital
loads, possibly in more than one train.
This information notice requires no specific action or written response. If
you have any questions about the information in this notice, please contact
one of the technical contacts listed below or the appropriate Office of
Nuclear Reactor Regulation (NRR) project manager.
Brian K. Grimes, Director
Divis4on of Operating Reactor Support
Office of Nuclear Reactor Regulation
Technical contacts: Stephen D. Alexander, NRR
(301) 504-2995 Kamalakar R. Naidu, NRR
(301) 504-2981 Attachment:
List of Recently Issued NRC Information Notices
a
Attachment
In 93-75 September 17 1993 Page I of I
49) 0,
IB 3 U faf
4C f*
LIST OF RECENTLY ISSUED
NRCINFORNATION NOTICES
Informatlon Date Ot
Notice No. Subject Issuance Issued to
2
93-74 High Temperatures Reduce 09/16/93 All holbers of OLs or CPs
Limitorque AC Motor for nuclear power reactors.
Operator Torque
93-73 Criminal Prosecution of 09/15/93 All KRClicensees.
Nuclear Suppliers for
Wrongdoing
93-72 Observations from Recent 09/14/93 All holders of OLs or CPs
Shutdown Risk and Outage for nuclear power reactors.
Nanagement Pilot Team otu
Inspections
93-71 Fire at Chernobyl Unit 2 09/13/93 All holders of OLs or CPs
for nuclear power reactors.;
to a cco
93-70 Degradation of Boraflex 09/10/93 All holders of OLs or CPs
Neutron Absorber Coupons for nuclear power reactors.
93-69 Radiography Events at 09/02/93 All holders of OLs or CPs
Operating Power Reactors for nuclear power reactors
and all radiography
licensees.
93-68 Failure of Pump Shaft 09/01/93 All holders of OLs or CPs
Coupling Caused by for nuclear power reactors.
Temper Embrittlement
during Nanufacture
) 92-16, Supp. 2 Loss of Flow from the
Pump during Refueling
08/23/93 All holders of OLs or CPs
for nuclear power reactors.
Cavity Draindown
93-67 Bursting of High 08/16/93 All holders of OLs or CPs i"
Pressure Coolant for nuclear power reactors. 2o
Injection Steam Line 0z V
Rupture Discs Injures
Plant Personnel f 0
Q
C*
OL - Operating License 41 h-J
°e
- Construction Permit
0.
z
IN 93-75 September 17, 1993 molded-case circuit breakers, and "Power Break" circuit breakers in addition
to the metalclad breakers. Although, none except those on metalclad air
circuit breakers have reportedly experienced this problem, other RMS-9s may
not have been exposed to the transients of concern. Meanwhile, GE NE and the
GE Switchgear Apparatus Service Shop in Atlanta, Georgia, are currently
assisting Maine Yankee in exchanging (at least temporarily) several critical
RMS-9-equipped breakers for ones fitted with EC-type series trip units.
In terms of safety significance, these incidents of spurious tripping, although somewhat isolated, raise the concern that a common-mode initiator of
intermittent ground faults on nonsafety-related and unqualified circuits, such
as a loss-of-coolant accident or high-energy line break, could conceivably
cause propagation of current spikes to multiple portions of an electrical
distribution system. They may not trip Class 1E isolation breakers not fitted
with RMS-9s, and may not trip some with RMS-9s, but could result in unwanted
tripping of other RMS-9-equipped breakers and the attendant loss of vital
loads, possibly in more than one train.
This information notice requires no specific action or written response. If
you have any questions about the information in this notice, please contact
one of the technical contacts listed below or the appropriate Office of
Nuclear Reactor Regulation (NRR) project manager.
orig /s/'d by AEChaffee/for
Brian K. Grimes, Director
Division of Operating Reactor Support
Office of Nuclear Reactor Regulation
Technical contacts: Stephen D. Alexander, NRR
(301) 504-2995 Kamalakar R. Naidu, NRR
(301) 504-2981 Attachment: List of Recently Issued NRC Information Notices
- See previous concurrence l
OFFICE VIB/DRIL VIB/DRIL SC/VIB/DRIL BC/VIB/DRIL TECHED
NAME SALEXANDER* KNAIDU* GCWALINA* LNORRHOLM* DGABLE*
DATE 8/05/93 8/05/93 8/11/93 8/11/93 8/06/93 YES YES YES YES NO
COPY
OFFICE D/DRIL/NRR BC/SELB/DEST BC/OGCB/DORS D DORS
NAME CEROSSI* CBERLINGER* GMARCUS* BK~k
DATE 8/13/93 8/13/93 8/23/93 9/1 //93 YES YES NO YES NO YES NO
COPY YES 01-7r, IN
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\~d IN 93-75 September 17, 1993 molded-case circuit breakers, and "Power Break" circuit breakers in addition
to the metalclad breakers. Although, none except those on metalclad air
circuit breakers have reportedly experienced this problem, other RMS-9s may
not have been exposed to the transients of concern. Meanwhile, GE NE and the
GE Switchgear Apparatus Service Shop in Atlanta, Georgia, are currently
assisting Maine Yankee in exchanging (at least temporarily) several critical
RMS-9-equipped breakers for ones fitted with EC-type series trip units.
In terms of safety significance, these incidents of spurious tripping, although somewhat isolated, raise the concern that a common-mode initiator of
ground faults on nonsafety-related and unqualified circuits, such as a loss- of-coolant accident or high-energy line break, could conceivably cause
propagation of current spikes to multiple portions of an electrical
distribution system. They may not trip Class lE isolation breakers not fitted
with RMS-9s, but could result in unwanted tripping of RMS-9-equipped breakers
and the attendant loss of vital loads, possibly in more than one train.
This information notice requires no specific action or written response. If
you have any questions about the information in this notice, please contact
one of the technical contacts listed below or the appropriate Office of
Nuclear Reactor Regulation (NRR) project manager.
Brian K. Grimes, Director
Division of Operating Reactor Support
Office of Nuclear Reactor Regulation
Technical contacts: Stephen D. Alexander, NRR
(301) 504-2995 Kamalakar R. Naidu, NRR
(301) 504-2981 Attachment: List of Recently Issued NRC Information Notices
- See Drevious concurrence
OFFICE VIB/DRIL VIB/DRIL SC/VIB/DRIL BC/VIB/DRIL TECHED
NAME SALEXANDER* KNAIDU* GCWALINA* LNORRHOLM* DGABLE*
DATE 8/05/93 8/05/93 8/11/93 8/11/93 8/06/93 COPY YES YES YES YES NO
OFFICE D/DRIL/NRR BC/SELB/DEST BC/OGCB/DORS _DO_ _ _
NAME CEROSSI* CBERLINGER* GMARCUS* BKGK S /93ES
DATE 8/13/93 8/13/93 8/23/93 9 93 / /93 COPY YES YES YES NO YES NO YES NO
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IN 93-XX
September XX, 1993 are currently
GE Switchgear Apparatus Service Shop in Atlanta, Georgia, several critical
assisting Maine Yankee in exchanging (at least temporarily)
fitted with EC-type series trip units.
RMS-9-equipped breakers for ones
tripping, In terms of safety significance, these incidents of spurious initiator of
although somewhat isolated, raise the concern that a common-mode
such as a loss- ground faults on nonsafety-related and unqualified circuits, cause
of-coolant accident or high-energy line break, could conceivably
propagation of current spikes to multiple portions of an electrical breakers not fitted
distribution system. They may not trip Class IE isolation breakers
with RMS-9s, but could result in unwanted tripping of RMS-9-equipped than one train.
and the attendant loss of vital loads, possibly in more
response. If
This information notice requires no specific action or writtenplease contact
you have any questions about the information in this notice, Office of
one of the technical contacts listed below or the appropriate
Nuclear Reactor Regulation (NRR) project manager.
Brian K. Grimes, Director
Division of Operating Reactor Support
Office of Nuclear Reactor Regulation
Technical contacts: Stephen D. Alexander, NRR
(301) 504-2995 Kamalakar R. Naidu, NRR
(301) 504-2981 Attachment: List of Recently Issued NRC Information Notices
- See previous concurrence
VIB/DRIL VIB/DRIL SC/VIB/DRIL BC/VIB/DRIL TECHED
OFFICE
SALEXANDER* KNAIDU* GCWALINA* LNORRHOLM* DGABLE*
NAME
8/05/93 8/05/93 8/11/93 8/11/93 8/06/93 DATE
YES YES YES NO
COPY YES
OFFICE D/DRIL/NRR BC/SELB/DEST BC/OGCB/DORS D/DORS____l
NAME CEROSSI* CBERLINGER* GMARCUS9 BKGRIMES
8/13/93 8/13/93 /93 9/ /93 / /93 DATE
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IN 93-XX
August XX, 1993 In terms of saf significance, these incidents of spurious tripping, although somewhat olated, raise the concern that a common-mode initiator of
ground faults on non fety-related and unqualified circuits, such as a loss- of-coolant accident or igh-energy line break, could conceivably cause
propagation of current stkes to multiple portions of an electrical
distribution system. They ay not trip Class 1E isolation breakers not fitted
with RMS-9s, but could resul in unwanted tripping of RMS-9-equipped breakers
and the attendant loss of vita loads, possibly in more than one train.
This information notice requires X specific action or written response. If
you have any questions about the inf mation in this notice, please contact
one of the technical contacts listed b ow or the appropriate Office of
Nuclear Reactor Regulation (NRR) project anager.
\1/
Brian K. imes, Director
Division o perating Reactor Support
Office of Nuc ear Reactor Regulation
Technical contacts: Stephen D. Alexander, NRR
(301) 504-2995 Kamalakar R. Naidu, NRR
(301) 504-2981 Attachment: List of Recently Issued NRC Information Notices
- Cne n-^%Aiorl ennenollrranr
OFFICE VIB/DRIL VIB/DRIL SC/VIB/DRIL BC/VIB/DRIL TECHED
NAME SALEXANDER* KNAIDU* GCWALINA* LNORRHOLM* DGABLE*
DATE 8/05/93 8/05/93 8/11/93 8/11/93 8/06/93 COPY YES YES YES YES NO
OFFICE D/DRIL/NRR BC/SELB/DEST BPRt_ D/DORSi
NAME CEROSSI* CBERLINGER* k7! ARCUS BKGRIMES
DATE 8/13/93 8/13/93 __ /_938/
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OFFICIAL RECKR LUPY WUtUMEM I n14nc1 .- n%1l1.7 n o
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IN 93-XX
August XX, 199:.3 In terms of safety sig *ficance, these incidents of spurious tripping, although somewhat isolate, raise the concern that a common-mode initiator of
ground faults, such as a 1 s-of-coolant accident or high-energy line break, could conceivably cause prop ation of current spikes to multiple portions of
an electrical distribution sys em, which could result in spurious tripping of
RMS-9-equipped breakers and the ttendant loss of vital loads, possibly in
more than one train.
This information notice requires no ecific action or written response. If
you have any questions about the infor tion in this notice, please contact
one of the technical contacts listed be w or the appropriate Office of
Nuclear Reactor Regulation (NRR) project nager.
\l/
Brian K. mies, Director
Division o Operating Reactor Support
Office of Nu lear Reactor Regulation
Technical contacts: Stephen D. Alexander, NRR
(301) 504-2995 Kamalakar R. Naidu, NRR
(301) 504-2981 Attachment: List of Recently Issued NRC Information Notices
- See previous concurrence
OFFICE VIB/DRIL VIB/DRIL SC/VIB/DRIL BC/VIB/DRIL TECHED
NAME SALEXANDER* KNAIDU* GCWALINA* LNORRHOLM* DGABLE*
DATE 8/05/93 8/05/93 8/11/93 /11/93 8/06/93 COPY YES YES YES YES NO
OFFICE D/DRIL/NRR BC/SELB/DEST 4,BC/OGCB/DORS XD/DORS
NAME CEROSSI* CBERLINGER* of2"MARCUS / BKGRIMES
DATE 8/13/93 8/13/93 e_ 8/ /93 _8_ /_/93
_93 COPY YES YES YES NO YES NO YES NO
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wuuVLqcn I 11MI-I. FM1Q1W I1% LIs . air9 OFFIIAL McUKU LuVY
IN 93-XX
August XX, 1993 This information notice quires no specific action or written response. If
you have any questions abot the information in this notice, please contact
one of the technical contact listed below or the appropriate Office of
Nuclear Reactor Regulation (NR project manager.
B an K. Grimes, Director
Div ion of Operating Reactor Support
Offic of Nuclear Reactor Regulation
Technical contacts: Stephen D. Alexander,
(301) 504-2995 Kamalakar R. Naidu, NRR
(301) 504-2981 Attachment: List of Recently Issued NRC Information Not
- See previous concurrence
OFFICE VIB/DRIL VIB/DRIL SCAV~RIL BCB/DRIL TECHED
SALEXANDER* KNAIDU* G L OAOLM _ DGABLE*
NAME
8/05/93 8/05/93 8/1 /93 8/l/93 8/06/93 DATE
COPY YES YES YES YES NO NO
OFFICE D/DRUIER,. BC/SELB/D0 BC/OGCB/DORS D/DORSl
NAME C ACBERLINGEV GMARCUS BKGRIMES
DATE 8/1,393 8/L5/93 8/ /93 ll
YES NO YES NO YES NO YES NO YES NO
COPY LAMC. OMCOTDTD TN
rhrINAEUT rvlloJ7Ir . GoLI
Id
OFFICIAL RECORD COPY UUuVrLcr1 I 11PULc.
K- -,
IN 93-XX
August XX, 1993 addition, the NRC has ned that certain early versions of the RMS-9 units
had instantaneous trip fu tions that could not be bypassed or the time delay
adjusted, indicating a poss e misapplication problem.
The NRC is attempting to btain sufficient information to better define
the range of applications of the units, envelope the conditions likely to
make the equipment susceptible to e problem, and identify any common-mode
initiators that may exist. GE Nucle Energy personnel, associated with GE's
Switchgear Apparatus Service Shop in A anta, Georgia, have informed the NRC
that GE is developing a modification for he RMS-9 circuitry to correct the
problem. GE also explained that its evidene suggests that ungrounded and/or
delta-connected (grounded or ungrounded) systms are most susceptible to the
kind of transients to which the RMS-9s can sp iously respond. GE is
currently assisting Maine Yankee in exchanging t least temporarily) RMS-9- equipped breakers for ones fitted with EC-type se *es overloads.
Meanwhile, the incidents of spurious tripping, although isolated, raise
the concern that a common-mode initiator of ground fai ts such as a loss-of- coolant accident or high-energy line break could conce ably cause propagation
of short-duration, high-current transients to multiple p itlons of an
electrical distribution system which could result in spurnus tripping of
RMS-9-equipped breakers and the attendant loss of vital loa, possibly in
more than one train. This information notice requires no spe ific action or
written response. If you have any questions about the informa on in this
notice, please contact one of the technical contacts listed bela or the
appropriate Office of Nuclear Reactor Regulation (NRR) Project Ma ger.
Brian K. Grimes, Director
Division of Operating Reactor Support
Office of Nuclear Reactor Regulation
Technical contacts: Stephen D. Alexander, NRR (301) 504-2995 Kamalakar R. Naidu, NRR (301) 504-2981 Attachment: List of Recently Issued NRC Information Notices
- See previous concurrence
OFFICE VIB/DRIL VIB/DRIL BC RIL TECHED
NAME SALEXANDER* KNAIDU* A --AV M DGABLE*
DATE 8/05/93 8/05/93 //938/ 6 /93 8/06/93 COPY YES YES YES YES NO NO
OFFICE D/ L/NRR BC/SELB/DEST BC/OGCB/DORS D/DORS
NAME C CBERLINGER GMARCUS BKGRIMES
DATE 8/( /93 8/ /93 8/ /93 /93 COPY YES NO YES NO YES NO YES NO YES NO
UII-ILIAL ------ Idler.
-L--T-rlL: 1uc4TnT
OFFICIAL RECORD LUPY UUUMLN I NANL: WZ)VIK1FPAN
IN 93-XX
August XX, 1993 and Control in ainville, Connecticut) providing trip units that are less
sensitive to high mplitude, short-duration current transients. However, the
NRC has learned tha certain early versions of the RMS-9 units had
instantaneous trip fu tions that could not be bypassed or the time delay
adjusted indicating als a potential misapplication problem.
The NRC is attempti to obtain sufficient information to better define
the range of applications o these units, envelope the conditions likely to
make the equipment susceptibl to the problem, and identify any common mode
initiators that may exist. GE uclear Energy personnel associated with GE's
Atlanta, Georgia, Switchgear App atus Service Shop have informed the NRC that
GE is developing a modification fo the RMS-9 circuitry to correct the
problem. GE also explained that its vidence suggests that ungrounded and/or
delta-connected (grounded or ungrounde systems are most susceptible to the
kind of transients to which the RMS-9s n spuriously respond. GE is also
currently assisting Maine Yankee in excha ing (at least temporarily) RMS-9- equipped breakers for ones fitted with EC tye series overloads.
Meanwhile, the incidents of spurious tiping, although isolated, raise
the concern that a common-mode initiator of gr nd faults such as a loss-of- coolant accident or high-energy line break coul conceivably cause propagation
of short-duration, high-current transients to mul tile portions of an
electrical distribution system which could result i spurious tripping of
RMS-9-equipped breakers and the attendant loss of vit 1 loads, possibly in
more than one train.
This information notice requires no specific actio or written response.
If you have any questions about the information in this n ice, please contact
one of the technical contacts listed below or the appropria Office of
Nuclear Reactor Regulation (NRR) Project Manager.
Brian K. Grimes, Director
Division of Operating Reactor Support
Office of Nuclear Reactor Regulation
Technical contacts: Kamalakar R. Naidu, NRR (301) 504-2981 Stephen D. Alexander, NRR (301) 504-2995 Attachment: List of Recently Issued NRC Information Notices
OFFICE VIB/DRIL VIB/DRIL SC/VIB/DRIL BC/VIB/DRIL TECHED
NAME KNAIDU SALEXANDER GCWALINA LNORRHOLM
8/ /93 8/ /93 8/ /93 8/ /93 8/6 /93 DATE
COPY YES YES YES YES NO NO
OFFICE D/DRIL/NRR BC/SELB/DEST BC/OGCB/DORS D/DORSl
NAME CEROSSI CBERLINGER GMARCUS BKGRIMES
DATE 8/ /93 8/ /93 8/ /93 8/ /93 /93 YES NO YES NO YES NO YES NO YES NO
COPY
IN 93-XX
August XX, 1993 and Control in ainville, Connecticut) providing trip units that are less
sensitive to high mplitude, short-duration current transients. However, the
NRC has learned tha certain early versions of the RMS-9 units had
instantaneous trip funtions that could not be bypassed or the time delay
adjusted indicating als a potential misapplication problem.
The NRC is attempt g to obtain sufficient information to better define
the range of applications these units, envelope the conditions likely to
make the equipment susceptib e to the problem, and identify any common mode
initiators that may exist. G Nuclear Energy personnel associated with GE's
Atlanta, Georgia, Switchgear Aplaratus Service Shop have informed the NRC that
GE is developing a modification r the RMS-9 circuitry to correct the
problem. GE also explained that i evidence suggests that ungrounded and/or
delta-connected (grounded or ungroun ed) systems are most susceptible to the
kind of transients to which the RMS-9:can spuriously respond. GE is also
currently assisting Maine Yankee in exc anging (at least temporarily) RMS-9- equipped breakers for ones fitted with E type series overloads.
Meanwhile, the incidents of spurious tripping, although isolated, raise
the concern that a common-mode initiator o round faults such as a loss-of- coolant accident or high-energy line break c ld conceivably cause propagation
of short-duration, high-current transients to ultiple portions of an
electrical distribution system which could resu t in spurious tripping of
RMS-9-equipped breakers and the attendant loss o vital loads, possibly in
more than one train.
This information notice requires no specific ction or written response.
If you have any questions about the information in t is notice, please contact
one of the technical contacts listed below or the app priate Office of
Nuclear Reactor Regulation (NRR) Project Manager.
1//
Brian K. Grimes, Director
Division of Operating Reactor Support
Office of Nuclear Reactor Regulation
Technical contacts: Kamalakar R. Naidu, NRR (301) 504-2981 Stephen D. Alexander, NRR (301) 504-2995 Attachment: List of Recently Issued NRC Information Notices
OFFICE IB IL lVIB/DRIL , SC/VIB/DRIL BC/VIB/DRIL TECHED
NAME KNAW A o- SALEXANDER GCWALINA LNORRHOLM
DATE 8/6&/93 8/ /93 8/ /93 8/ /93 COPY YES YES YES YES NO NO
OFFICE D/DRIL/NRR BC/SELB/DEST BC/OGCB/DORS D/DORS
NAME CEROSSI CBERLINGER GMARCUS BKGRIMES
DATE 8/ /93 8/ /93 8/ /93 8/ /93 /93 COPY YES NO YES NO YES NO YES NO YES NO